1. Field of the Invention
The present invention relates to an image data encoding apparatus and decoding apparatus for extracting information on characteristic points of image data and compressing and expanding the image data based on the information of the characteristic points.
2. Description of the Related Art
One of the methods conventionally used for compressing and encoding moving picture data has been the MPEG (Moving Picture Coding Experts Group) standard.
When encoding color moving picture data by the MPEG standard, moving compensation processing is performed using the luminance signal Y among the luminance signal Y and chrominance signals U and V.
Further, discrete cosine transformation (DCT) processing is performed independently on the residual signals of the luminance signal Y and chrominance signals U and V.
In usual transformation and encoding systems of moving picture data such as the MPEG standard explained above, positive utilization has not been made of the close correlation between the luminance signal Y element and chrominance signal U and V elements constituting the moving picture data or among the red signal (R) element, green signal (G) element, and blue signal (B) element despite the existence of that correlation.
Further, at the characteristic points, such as the edges between one object and another in a picture, generally the luminance signal (Y) element and chrominance signal (U, V) elements of the moving picture data and color signal (R, G, B) elements have a very close relationship with each other.
Even in an encoding system for moving picture data using for example the positional information of the above characteristic points of moving picture data, for example, an encoding system using wavelets, there is still not known any system which makes positive utilization of the correlation between the luminance signal element and chrominance signal elements, or among the color signal elements.